The major objective of the proposed research is to examine the effects of bilateral and right electroconvulsive therapy (ECT) on affective and cognitive functioning. The consequences of the two treatment modes will be studied in regard to neuropsychological functions that previously have not been investigated and in traditional areas of inquiry. Review of the literature on the role of functional brain asymmetry in the regulation of emotion and on the comparative effects of ECT treatment modes suggests that functional brain asymmetry mediates both the affective and cognitive consequences of treatment. The proposed research is designed to further elucidate the effects of treatment modes on lateralized neuropsychological functions. Drug-free inpatients presenting major, unipolar depressive disorder will be tested before, during, and after treatment, and a matched normal control group will be tested at comparably spaced times. Differences between depressed patients and controls at pretreatment assessment will be examined, as well as the time-courses of the effects of treatment. Posttreatment assessments include a two-month followup and retesting a sample of relapsed and nonrelapsed patients. The interrelations among the therapeutic and other effective consequences of treatment and cognitive effects will be examined. Patterns of brain asymmetry in effective and cognitive functioning that predict response to bilateral and right ECT will also be reported.